Facts To Know About US Open 2013

For the first time, Andy Murray will be the defending champion at a Grand Slam tournament - and he suspects he'll be more nervous than usual in the early rounds. His championship at the 2012 US Open made him the first man from Britain to win a major title since Fred Perry in 1936. (Photo: Getty Images)

Rafael Nadal has gone through all manner of ups and downs over the past two seasons, including a seven-month absence because of knee trouble that forced him to miss last year's US Open. He's looked terrific lately, improving to 15-0 on hard courts in 2013 by winning Montreal and Cincinnati titles. (Photo: AP)

Roger Federer's 17 Grand Slam titles include five at the US Open. He was ranked No. 1 for more weeks than any man in history. He was seeded No. 1 at 18 consecutive Grand Slam tournaments from 2004-08. However, this time he is seeded No. 7 at the US Open and a possible quarterfinal clash with Nadal is on the cards. (Photo: Getty Images)

The so-called Big 4 of Federer, Nadal, Djokovic and Murray have combined to win 33 of the past 34 Grand Slam titles. Any discussion of other contenders must begin with the guy who kept it from being 34 of 34 - Juan Martin del Potro, who surprised Federer at the 2009 US Open. (Photo: AP)

This US Open is the 40th Grand Slam tournament since an American man won a major title, Andy Roddick's at Flushing Meadows in 2003. John Isner, who is listed at 6-foot-10 and can serve as well as anyone, is seeded 13th and could play Nadal in the fourth round. (Photo: AP)

For all Serena Williams has accomplished, one tiny thing missing from her resume is a successful title defense at the US Open. She won her fourth trophy at Flushing Meadows last year, edging No. 2 Victoria Azarenka in a gripping three-set final. But Azarenka believes she has a chance against Williams. (Photo: AP)

Maria Sharapova surprisingly withdrew the day before the draw, leaving the field without a four-time Grand Slam champion and TV broadcasters without one of the sport's top stars. Wimbledon champion Marion Bartoli isn't entered in the US Open, either, and it's because she suddenly announced her retirement. (Photo: Reuters)

Sloane Stephens is seeded 15th, and the sport's biggest stages bring out her best tennis: She upset Williams en route to the Australian Open semifinals, made it to the Wimbledon quarterfinals before losing to eventual champion Bartoli, and got to the second week at the French Open, too. (Photo: Getty Images)

For the first time in the Open era, which began in 1968, the year's last Grand Slam tournament is scheduled to end on a Monday - a result of the push by top players to provide a day of rest between the men's semifinals and final, instead of the US Open's long-standing Saturday-Sunday finish. (Photo: Getty Images)